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CHAPTER 18 Concrete Flatwork and Formed Shapes

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Place concrete forms. Perform finishing operations, including screeding, edging and jointing, floating, brooming, and form removal. Describe three basic types of joints used in concrete construction. Build a variety of patterns, textures, and decorative finishes into concrete during construction. Objectives

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Describe how cast-in-place concrete is used in walls and roof and floor systems. Describe the construction of precast/prestressed concrete systems. Objectives (Cont.)

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Considerations: National, state, and local codes Intended use or uses Type of finish on surface of concrete Color to be added to concrete Weight that will be supported Planning Concrete Projects

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Concrete is moved from a delivery truck to its final location by a variety of methods Handled by cranes or pumping through pipes Method should not restrict consistency of concrete Placing and Finishing Concrete

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Preparation Properly prepare before concrete arrives Subgrade should be smooth, compacted, and moistened Forms should be leveled and braced Portland Cement Association

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Remove any cement from forms Treat forms with oils or release agent Reinforcing steel should be clean and free of loose rust and scale Preparation (Cont.)

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Place as near as possible to intended location Do not place in large quantities in one area, allow to run, or work over a long distance Place in horizontal layers of uniform thickness Placing Concrete

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Placing Concrete (Cont.) In deep forms, compact or vibrate after each layer is placed Should not drop freely more than 3 to 4 On large projects, concrete pump truck pushes concrete through hose attached to boom John Cooke/iStock/Thinkstock Dmitry Kalinovsky/Shutterstock.com

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Determine size and location of slab Excavate area to appropriate depth and slope Construct forms for concrete slab Place reinforcement if required or needed Determine amount and type of concrete and order for delivery Slab Construction

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Place concrete inside forms Level concrete in forms (screed) If bleed water appears, wait until it evaporates Edge, joint, and float concrete slab Trowel the surface Texture surface if needed Cure concrete Slab Construction (Cont.)

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Slab Construction (Cont.) Start at most distant point of work Prevent stone pockets Place around perimeter first in large flat open areas Do not allow water to collect at ends or corners of forms

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Necessary to eliminate stone or air pockets and consolidates each layer with previously placed layer Brings fine material to face and top for proper finishing Mechanical vibrators can be used Compacting the Concrete

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Good bond and watertight joint are important Hardened concrete should be reasonably level, rough, clean, and moist Some exposed coarse aggregate aids bonding Remove loose or soft mortar before placing fresh batch of concrete Placing on Hardened Concrete

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Mixture of Portland cement, aggregate, and water shot into place by compressed air Applied by either wet or dry mix process In dry mix process, cement and aggregates are mixed in a relatively dry condition In wet mix process, concrete is premixed Person directing nozzle controls thickness of concrete layer and angle of application Shotcrete

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Finishing process depends on effect desired Some surfaces are left rough Others are broomed, floated, or troweled Can be textured, colored, or have exposed aggregate Finishing Concrete Slabs

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Screeding First finishing operation after concrete is placed Striking off excess concrete to bring top surface to proper grade or elevation Wood and magnesium screeds are used Sharon Meredith/iStock/Thinkstock

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Prior to placement, determine final height with snap lines or laser level Power screeds are used for larger jobs Vibrations drive surface stones down and bring cream to top Screeding (Cont.)

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Concrete Against Interior Walls Hand trowel or float concrete next to wall Marshalltown Company

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Floating Concrete Float before bleed water surfaces Bleeding occurs when dry materials begin to sink or settle or if too much water is added during mixing Use bull float or darby to eliminate high and low spots Vicki Reid/iStock/Thinkstock

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Edging Provides a rounded edge or radius Prevents chipping or damage to the edge Cover all coarse aggregate Stanley Goldblatt

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Jointing Cuts groove in slab Control joint Contraction joint Cracks occur at joint where they are not noticeable Stanley Goldblatt

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Spaced at intervals equal to width of slab, not more than 10 apart Joints should be perpendicular to edge Wood or magnesium straightedge is used as guide Large concrete surfaces can be jointed by cutting grooves Sidewalk and Driveway Joints

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Three reasons why concrete is floated To embed aggregate particles just beneath surface To remove slight imperfections, waves, and voids To compact the concrete at the surface Surface is floated with wood or metal floats or with a finishing machine using float blades Floating

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Troweling Produces smooth, dense, hard surface During first troweling, keep blade as flat against surface as possible Surface can be troweled several times to obtain desired finish Done by hand or machine Ari N/Shutterstock.com

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Brooming Produces a slightly roughened surface Draw soft-bristled push broom over surface Broom perpendicular to traffic to provide most resistance

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Form Removal Leave forms in place until concrete is: Strong enough to support its own weight and loads Hard enough to resist damage from form removal Test concrete to determine hardness

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Use only wooden wedges Do not place pinch bar against concrete to wedge forms loose Start removing forms some distance from a projection Form Removal (Cont.)

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. No waiting for evaporation of free water from surface before floating and troweling Use aluminum or magnesium float for hand floating Finishing Air-Entrained Concrete

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Curing Concrete Protect new concrete from sun and do not allow it to dry too fast Keep coverings moist for at least three days Other curing methods Ponding Membrane curing compounds Portland Cement Association

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Rate of chemical reaction between cement and water is affected by temperature According to American Concrete Institute, cold weather is considered to be air temperature that averages less than 40F and is below 50F more than half of each day for three weeks in a row Curing Temperatures

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Cold Weather Construction Concrete placement may require: Heated materials Covering for fresh concrete Heated enclosure Jack Klasey

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Cold Weather Construction (Cont.) Temperature of concrete at time of placing should generally be 50F to 70F Never heat materials above 70F If concrete freezes before it hardens, compressive strength is decreased Never place concrete on frozen subgrade Thawed subgrade should be recompacted Place thin layer of warm concrete on cold, hardened concrete when upper layer is to be poured

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Cold Weather Construction (Cont.) Maintain temperature of normal concrete at 70F for three days or 50F for five days Keep temperature of high early-strength concrete at 70F for two days or 50F for three days Do not allow concrete to freeze for next four days Shorten set time by ordering concrete with extra cement, Type III cement, chemical accelerators, or a combination

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Insulation Straw Insulating blankets Tent or heated enclosure Properly vent for safety Cold Weather Protection

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Concrete sets much faster Cracked or poorly finished slabs Loses slump faster Can become unworkable before large load can be placed Hot Weather Construction

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Saturate subgrades some time in advance and sprinkled just ahead of placing concrete Wood forms should be treated and wetted Concrete should be screeded and darbied immediately after placing Keep covers constantly wet Hot Weather Construction (Cont.)

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Cool mixing material with chilled water or ice Ice should be melted before concrete leaves mixer Get an early start while it is cooler Break big placements into smaller sections Shade the operation if practical Use additives Preventing Rapid Drying

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Moisture for Curing Curing can continue for 28 days Moisture must be present for at least 7 days Air-entrained concrete requires special expertise Ways to trap moisture: Spraying liquid curing compound Ponding, sprinkling, or fogging Covering concrete with plastic Applying wet sand, hay, or burlap over surface

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Joints in Concrete Isolation joints separate parts of structure Permit both vertical and horizontal movements Control joints compen- sate for contraction due to shrinkage

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Construction joints provide for no movement across joint Stopping places in the process of casting Joints in Concrete (Cont.)

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Color Exposed aggregates Textured forms Ground concrete for polished finish Scored or stamped geometric patterns Divider strips Decorative and Special Finishes

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. One-course method Two-course method Dry-shake method Amount of pigment should never exceed 10% of weight of cement Colored Concrete

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Exposed Aggregate Unlimited color selection Broad range of textures Rugged Slip resistant Immune to weather Wilm Ihlenfeld/Shutterstock.com

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Keep level of surface 3/8 to 1/2 lower than forms Fill space with extra aggregates Embed aggregate by tapping Work surface with hand float until surface is similar to that of normal slab after floating Seeding Method

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. When slab can bear workers weight without indentations, brush slab with stiff nylon bristle broom to remove extra mortar Apply fine spray of water along with brushing Continue until water is clear and there is no noticeable cement film left on aggregate Seeding Method (Cont.)

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Exposing stone in conventional concrete High proportion of coarse to fine aggregate Coarse aggregate should be uniform in size, bright in color, closely packed, and uniformly distributed Slump must be between 1 and 3 Terrazzo toppings Marble, quartz, or granite chips 1/2 thick Other Methods of Exposing Aggregate

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Textured Finishes Brooming Travertine finish Dash coat of mortar over freshly leveled concrete Rock salt Scattered over surface after hand floating or troweling

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Geometric Patterns Stamped, sawed, or scored into a concrete surface Enhances beauty of walks, drive, or patios Divider strips can be used to create patterns Bomanite Corporation

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Patterns and Colors Patterns such as stone, brick, or tile can be cut into partially set concrete with special stamping tools Color can also be added to create varying effects Stanley Goldblatt Keith Muratori/Shutterstock.com

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Begin after screeding and finishing are completed Apply color hardener on concrete surface Apply release agent Check surface Begin stamping in corner; work around perimeter Once perimeter is complete, go back to corner and begin first row of stamping Stamping Concrete

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Continue to stamp rows of concrete until slab is complete Complete joints by hand where stamping forms cannot access Remove residual concrete, extra release agent or curing compound, and any other foreign materials Stamping Concrete (Cont.)

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Continue to stamp rows of concrete until slab is complete Complete joints by hand where stamping forms cannot access Remove residual concrete and extra release agent or curing compound Stamping Concrete (Cont.)

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Install control joints Seal surface Stamping Concrete (Cont.) Imagenet/Shutterstock.com

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Applied to surfaces that are wet or dangerous if slippery Abrasive grains can be dry-shaken on surface and lightly troweled Spread uniformly over surface Use from 1/4 to 1/2 lb per sq ft of slab surface Nonslip and Sparkling Finishes

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Made with ready-mix concrete Structures of all shapes, sizes, and heights Exterior wall surfaces can be rough, smooth, natural, or colored Popular types are rustic, grid-patterned, colored aggregate, window walls, and sculptured Cast-in-Place Walls

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Rustic Concrete Walls Rough form boards Bush hammering Vertical fins

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Grid-Patterned Concrete Walls Well-planned joint patterns Tie holes KPG_Payless/Shutterstock.com

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Various methods Large percentage of coarse aggregate in mix; sandblast, bush hammer, or chisel-texture surface Place dry aggregate in form and then grout under pressure with cement-sand-water slurry Wrap wire mesh around reinforcement and preplace aggregate between mesh and outside form Colored Aggregate Surfaces

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Cast-in-Place Window Walls White Portland cement Coarse aggregate reasonably uniform in color Plastic forms are reinforced with fiberglass ASG Corporation

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Sculptured Concrete Walls Wide range of material can be used to form decorative patterns Plaster waste molds can be used for fine sculpturing

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Cast-in-Place Concrete Roof and Floor Systems Pan joist construction One-way structural system Reusable forming pans Waffle pans Form ceiling between levels of one floor and another

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Cast-in-Place Concrete Roof and Floor Systems (Cont.) Flat plate system Minimum depth and architectural simplicity Two-way reinforced concrete framing system Flat slab system Heavy roof loads with large open bays below Supporting panel in area of each column

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Tilt-up panels, standard-shaped concrete panels, or concrete window walls Variety of prestressed panels and shapes are used in wall, roof, and floor systems Trained and competent individuals required for handling and installation OSHA safety standards must be followed Precast/Prestressed Concrete Systems

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Process of casting concrete walls in horizontal position on-site or in another location Advantages: reasonable cost, low maintenance, durability, and speed of construction Suited for buildings greater than 10,000 sq ft with 20 or higher side walls that incorporate repetition in panel size and appearance Tilt-Up Construction

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Tilt-Up Construction (Cont.) Panel connections are determined before construction Reinforcement is designed to accommo- date lifting loads Drawing of each panel shows front, back, and inserts embedded

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Most tilt-up buildings use spread footings Footings must be straight and smooth Tilt-Up Construction (Cont.)

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Cast as individual panels or as larger slabs sawed into smaller panels after concrete has been placed Grid of reinforcing steel Many are cast with a textured surface or pattern Tilt-Up Panels

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Braces are attached before panels are lifted and not removed until roof and decking are installed Tilt-Up Panels (Cont.)

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Lifting Panels into Place

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Prestressed Panels Crack-free and resistant to deterioration Common designs Double-tee units Single-tee units Hollow-core panels Double-Tee Units

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Double-Tee and Single-Tee Units Double-tee units Spans up to 60 are possible with the 4 wide unit, greater spans possible with wider units Single-tee units Spans from 30 to 100 Single-tee units are placed flange to flange or spread apart with concrete plants or cast-in-place concrete

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Cored Slabs Provide a flush ceiling with minimum depth required for roof or floor system

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Copyright Goodheart-Willcox Co., Inc. May not be posted to a publicly accessible website. Cast as curtain walls or loadbearing walls One-story or multistory May be preglazed Precast Concrete Window Walls Kawneer Company, Inc.